Phosphorescent ferro-magnetic particle formulation and method of non-destructive testing therewith

Patent metadata

Field	Value
Publication number	US-11313835-B2
Application number	US-201616084085-A
Country	US
Kind code	B2
Filing date	Dec 20, 2016
Priority date	Mar 11, 2016
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

A dispersion of particles is provided that each contain at least one ferromagnetic domain and at least one phosphor domain having a stimulation wavelength, a glow persistence of at least 5 seconds and a visible wavelength emission. A polymeric resin that is transmissive of the stimulation wavelength and the visible wavelength emission coats the ferromagnetic and phosphor domains to define each particle size. A method of non-destructively inspecting a test article applies a dispersion of these particles to a surface of the test article. A magnetic field is then induced including the test article. The surface of the test article is exposed to incident energy adapted to stimulate phosphorescence of the dispersion of particles. With the incident energy exposure ceased, the position of the dispersion of particles on the surface of the test article is imaged. An inspection system for non-destructively inspecting a test article is also provided.

First claim

The invention claimed is:

1. A dispersion of particles, each of the particles comprising:
at least one ferromagnetic domain, the at least one ferromagnetic domain having an average domain size of 1 to 50 microns;
at least one phosphor domain having a stimulation wavelength, a glow persistence of at least 5 seconds, and a visible wavelength emission; and
a polymeric resin coating that is transmissive of the stimulation wavelength and the visible wavelength emission, where said polymeric resin coating, said at least one ferromagnetic domain, and said at least one phosphor domain define a particle size, said polymeric resin coating firmly adherent to said at least one ferromagnetic domain and said at least one phosphor domain.

2. The dispersion of particles of claim 1 wherein said polymeric resin coating is one of: a polyamide, a melamine, a latex, an acrylic, a meth acrylic, a polyvinyl resin, or an epoxy.

3. The dispersion of particles of claim 1 wherein said polymeric resin coating is adapted to be UV cured.

4. The dispersion of particles of claim 1 wherein said at least one ferromagnetic domain comprises one of: γ-Fe 2 O 3 or magnetite with the formula Fe 3 O 4 .

5. The dispersion of particles of claim 1 wherein said at least phosphor domain comprises a metal present as a salt with an anion and an activator dopant.

6. The dispersion of particles of claim 5 wherein said anion is an oxide, a nitride, an oxynitride, a sulfide, a selenide, a halide or a silicate of said metal.

7. The dispersion of particles of claim 5 wherein said metal is zinc, cadmium, manganese, aluminum, silicon, a rare earth metal, or a combination thereof.

8. The dispersion of particles of claim 5 wherein said activator dopant is copper, manganese, a rare earth, or a combination thereof with the proviso that said activator dopant is not the same as said metal.

9. The dispersion of particles of claim 1 wherein the particle size is from 1 to 200 microns.

10. The dispersion of particles of claim 1 wherein the particle size is from 40 to 120 microns.

11. The dispersion of particles of claim 1 further comprising a fluorescent material.

12. A method of non-destructively inspecting a test article comprising:
applying the dispersion of particles of claim 1 to a surface of the test article;
inducing a magnetic field around the test article;
exposing the surface of the test article to incident energy adapted to stimulate phosphorescence of the dispersion of particles;
then stopping the incident energy exposure to the surface; and
then imaging the position of the dispersion of particles on the surface of the test article absent the incident energy exposure to non-destructively inspect the test article.

13. The method of claim 12 wherein said imaging is performed in darkness or under visible light.

14. The method of claim 12 wherein said incident energy source is ultraviolet light.

15. The method of claim 12 wherein said incident energy source is an electron beam source.

16. The method of claim 12 wherein said incident energy source is visible light and said imaging is performed in darkness.

17. The method of claim 12 wherein said applying is dry and absent a solvent, and the dispersion of particles has an average size of 40 to 120 microns.

18. The method of claim 12 wherein said applying is as a spray with a solvent, and the dispersion of particles has an average size of 1 to 60 microns.

19. An inspection system for non-destructively inspecting a test article comprising:
a tank having a volume containing a dispersion of particles of claim 1 ;
an applicator in fluid communication with the volume for transferring the dispersion of particles from said tank onto a surface of the test article;
an induction coil for magnetizing the test article;
an energy source for stimulating phosphorescence of the dispersion of particles; and
an inspection area remote from said energy source such that the dispersion of particles is not stimulated by said energy source in the inspection area.

20. The inspection system of claim 19 wherein said energy source is a laser that is incident on the volume of said tank.

Assignees

• Illinois Tool Works

Inventors

• Kilty Shawn Michael

Classifications

• G01N21/88

  Investigating the presence of flaws or contamination · CPC title

• C08F18/00

  Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid · CPC title

• C09K11/02

  Use of particular materials as binders, particle coatings or suspension media therefor · CPC title

• C09D177/02

  Polyamides derived from omega-amino carboxylic acids or from lactams thereof (C09D177/10 takes precedence) · CPC title

• H01F1/44

  of magnetic liquids, e.g. ferrofluids (particles in a bonding agent H01F1/28, H01F1/36, {H01F1/37}) · CPC title